Prognostic power of ventilatory responses during submaximal exercise in patients with chronic heart disease

The prognostic role of cardiopulmonary exercise testing in obesity

AIM

Poor cardiorespiratory fitness has been suggested to increase the risk of chronic diseases in obesity. We investigated the ability of key variables from cardiopulmonary exercise testing (CPET) to predict all-cause mortality in an obese cohort.

METHODS

The sample included 469 participants of both sexes (mean age 40 ± 13 years) who underwent a CPET for clinical reasons between 1 March 2009 and 1 December 2023. All-cause mortality was the prognostic endpoint. A receiver operating characteristic analysis was performed to establish optimal cut-points for CPET variables. Kaplan-Meier and Cox regression analyses were used to determine the association between CPET variables and all-cause mortality.

RESULTS

There were 46 deaths during a mean follow-up period of 69 ± 48 months, resulting in an annual mortality rate of 2%. Despite the sample being made up of mostly women (70%), there were more deaths in men (18 vs. 6%, p < 0.001).The optimal thresholds for discrimination of survival were as follows: (a) peak oxygen uptake (pVO2) ≤16 mL/kg/min; (b) minute ventilation/carbon dioxide production (VE/VCO2) slope ≥31; (c) ventilatory power ≤5.8 mmHg; and (d) circulatory power ≤2980 mmHg/mL O2/min. Kaplan-Meier survival plots revealed a significant positive association between lower pVO2, circulatory power and ventilatory power values and survival (log-rank, p < 0.001) and higher mortality for men than women. Adjusted Cox regression models showed that a pVO2 ≤16 mL/kg/min had a 20-fold higher risk of mortality when compared with >16 mL/kg/min.

CONCLUSION

Given the strong association of VO2, ventilatory efficiency, circulatory and ventilatory power with all-cause mortality, our findings support the notion that poorer cardiorespiratory fitness is associated with a poor prognosis in patients with obesity.

Relationship Between Increased Oxygen Uptake and Lactate Production With Progressive Incremental Electrode Skeletal Muscle Stimulation: A Pilot Study

Background Belt electrode skeletal muscle stimulation (B-SES) is an alternative exercise therapy for those with difficulty performing voluntary exercise. However, it is unknown whether oxygen uptake (VO2) in B-SES is comparable to cardiopulmonary exercise test (CPX) as assessed by voluntary exercise. This study aimed to evaluate oxygen uptake (VO2) and lactate (LA) production in incremental B-SES compared to ergometer CPX and to determine the relationship with ergometer CPX. Methods This study included 10 healthy young Japanese participants. Using a crossover design, all participants underwent incremental B-SES CPX and ergometer CPX using a 20 W ramp. Serum lactic acid concentration (LA) was measured serially before, during, and after B-SES. The tolerability of B-SES was adjusted with the change in LA level (⊿LA). Results Peak VO2 during B-SES (14.1±3.3 mL/kg/min) was significantly lower than ergometer peak VO2 (30.2±6.2 mL/kg/min, P<0.001). B-SES peak VO2 was similar to the anaerobic threshold (AT) VO2 on ergometer CPX (15.1±2.6 mL/kg/min). LA (Rest: 1.4±0.3, Peak: 2.8±0.8 mmol) and plasma noradrenalin (Rest: 0.2±0.1, Peak: 0.4±0.1 ng/mL) levels increased after B-SES. No significant correlation was observed between B-SES peak VO2 and ergometer CPX. However, after adjusting for B-SES, tolerability, it (peak VO2 of B-SES /⊿LA) correlated with peak VO2 (r=0.688, p=0.028) on the ergometer. Conclusion Peak VO2 of the passively progressive B-SES almost reached the AT value of the ergometer CPX without adverse events. Peak VO2 of B-SES adjusted with ⊿LA may be used to predict peak VO2 in ergometer CPX.

Pulmonary artery pressure-perfusion relation during exercise in patients with chronic thromboembolic pulmonary hypertension using pulmonary arteriography and right-heart catheterization

Background

In pulmonary hypertension (PH), pulmonary artery pressure (PAP) does not increase to pulmonary perfusion (PP) < 50%. During exercise, PAP may be increased even at PP > 50% for the early detection of PP disorders. The relationship between PP estimated by pulmonary angiography (PAG) and PAP was evaluated in patients with chronic thromboembolic PH (CTEPH) treated by balloon pulmonary angioplasty with near-normal PH.

Methods

Thirty-one patients (age 60 ± 11 years) with CTEPH underwent catheterization at rest and during exercise. Each segmental PP was determined by visualization of its segmental pulmonary artery and graded from 0 to 3 in the PAG. PP was estimated as the percentage PAG (%PAG) score-%summed total of all segmental PP/the full score-54.

Results

The mean PAP (mPAP) increased from 28 ± 6 mmHg to 46 ± 10 mmHg during exercise. Transpulmonary pressure gradient, the value of mPAP with the pulmonary artery wedge pressure substituted at peak exercise, was negatively correlated with %PAG score (rs = -0.56, p < 0.001) and elevated at > 50% PP.

Conclusions

The PAP-PP relationship at peak exercise was correlated, shifting from the relationship at rest, and the PAP started to rise with PP > 50%.

Correlation between acylcarnitine/free carnitine ratio and cardiopulmonary exercise test parameters in patients with incident dialysis

Objective: Diminished physical capacity is common and progressive in patients undergoing dialysis, who are also prone to deficiency in carnitine, which plays a pivotal role in maintaining skeletal muscle and cardiac function. The present study aimed to evaluate the association of carnitine profile with exercise parameters in patients with incident dialysis. Design and Methods: This was a single-center cross-sectional study including 87 consecutive patients aged 20-90 years who were initiated on dialysis in Keio University Hospital between December 2019 and December 2022 and fulfilled the eligibility criteria. Exercise parameters were evaluated via cardiopulmonary testing (CPX) using the electronically braked STRENGTH ERGO 8 ergometer, whereas the carnitine profile was assessed by determining serum free carnitine (FC), acylcarnitine (AC) levels and AC/FC ratio. Results: The mean cohort age was 62.1 ± 15.2 years, with male and hemodialysis predominance (70% and 73%, respectively). AC/FC was 0.46 ± 0.15, and CPX revealed peak oxygen consumption (VO₂) of 13.9 ± 3.7 (mL/kg/min) with percent-predicted peak VO₂ of 53.6% ± 14.7% and minute ventilation (VE)/carbon dioxide output (VCO₂) slope of 35.1 ± 8.0. Fully-adjusted multivariate linear regression analysis showed that AC/FC was significantly associated with decreased peak VO₂ (β, -5.43 [95% confidence interval (CI), -10.15 to -0.70]) and percent-predicted peak VO₂ (β, -19.98 [95% CI, -38.43 to -1.52]) and with increased VE/VCO₂ slope (β, 13.76 [95% CI, 3.78-23.75]); FC and AC did not exhibit similar associations with these parameters. Moreover, only AC/FC was associated with a decreased peak work rate (WR), percent-predicted WR, anaerobic threshold, delta VO₂/delta WR, and chronotropic index. Conclusion: In patients on incident dialysis, exercise parameters, including those related to both skeletal muscle and cardiac function, were strongly associated with AC/FC, a marker of carnitine deficiency indicating altered fatty acid metabolism. Further studies are warranted to determine whether carnitine supplementation can improve exercise capacity in patients on incident dialysis.

Impaired pulmonary and muscle function during moderate exercise in female patients recovered from SARS-CoV-2

This study aimed to assess pulmonary and muscle dysfunction by analyzing the slow component of oxygen uptake (VO2SC), and mechanical and ventilatory efficiency in adult women recovered from the severe acute respiratory syndrome coronavirus type II (SARS-CoV-2) during a constant load test. 32 women (N = 17 patients with SARS-CoV-2; N = 15 control group) performed two cardiopulmonary exercise tests (CPX) on a cycle ergometer. In the first test, the participants performed incremental CPX until extenuation. In the second test the participants performed a 10-min CPX at a constant load intensity (watts) corresponding to the first ventilatory threshold. There was a 48-72 h rest period between the two tests. There was a significant increase in the VO2SC in the patients recovered from SARS-CoV-2 (160.4 ± 60 mL min-1) in comparison with the healthy participants (59.6 ± 65 mL min-1) (P < 0.001). Mechanical efficiency significantly decreased in patients recovered from SARS-CoV-2 compared to the control group (P = 0.04). Ventilatory inefficiency significantly increased in the patients recovered from SARS-CoV-2 compared with the control group (P < 0.001). Adult women recovered from SARS-CoV-2 infection have important pulmonary and muscular dysfunction and fatigue which contributes to increasing the VO2SC and reducing mechanical and ventilatory efficiency during mild-moderate exercise at a constant load.

Factors contributing to exercise capacity in chronic thromboembolic pulmonary hypertension with near-normal hemodynamics

BACKGROUND

Despite improved survival for patients with chronic thromboembolic pulmonary hypertension (CTEPH) due to progressive medical and interventional treatment, impaired exercise capacity remains common due to poorly understood mechanisms. We aimed to clarify the exercise capacity of CTEPH patients with near-normal pulmonary hemodynamics and evaluate its determinants among the hemodynamic, peripheral (e.g., oxygen use by the peripheral tissues), and muscular (e.g., skeletal muscle strength) factors.

METHODS

Three hundred and twenty-nine patients with CTEPH (mean age, 63 ± 12 years; men/women, 73/256) with a near-normal mean pulmonary artery pressure (≤30 mm Hg) at rest were enrolled. We assessed exercise capacity by peak oxygen consumption (peak VO₂) using cardiopulmonary exercise testing with a right heart catheter. We also measured the 6-minute walk distance (6MWD) and quadriceps muscle strength.

RESULTS

The mean pulmonary artery pressure was 19 ± 4 mmHg and mean cardiac output was 4.8 ± 1.5 L/min at rest. The mean 6MWD was 444 ± 101 m, while the mean peak VO₂ was 14.4 ± 3.9 mL/min/kg. A multivariate model that predicted 6MWD included quadriceps strength (β = 0.45, p < 0.001) and peak arterial venous oxygen difference (β = 0.29, p < 0.001). In contrast, the peak VO₂ was best correlated with mPAP-CO slope (β = -0.30, p < 0.001), followed by quadriceps strength and peak arterial venous oxygen difference.

CONCLUSIONS

The 6MWD performance may be significantly influenced by peripheral oxygen use and muscular factors, while peak VO₂ is influenced by hemodynamic and peripheral factors in CTEPH patients with near-normal hemodynamics.

Exercise intolerance in chronic thromboembolic pulmonary hypertension after pulmonary angioplasty

INTRODUCTION

Exercise pulmonary hypertension is common in patients with chronic thromboembolic pulmonary hypertension (CTEPH) who experience shortness of breath during exercise and reduced exercise capacity despite normalised pulmonary arterial pressure (PAP) at rest; however, the relationship between exercise pulmonary hypertension and exercise capacity remains unclear. Here we aimed to determine whether exercise pulmonary hypertension is related to exercise capacity and ventilatory efficiency in CTEPH patients with normalised resting haemodynamics after pulmonary balloon angioplasty (BPA).

PATIENTS AND METHODS

In total, 249 patients with CTEPH treated with BPA (mean±sd age 63±14 years; male:female 62:187) with normal mean PAP (mPAP) (<25 mmHg) and pulmonary arterial wedge pressure (≤15 mmHg) at rest underwent cardiopulmonary exercise testing with right heart catheterisation. mPAP-cardiac output (CO) during exercise was plotted using multipoint plots. Exercise pulmonary hypertension was defined by a mPAP-CO slope >3.0.

RESULTS

At rest, pulmonary vascular resistance was significantly higher in the exercise pulmonary hypertension group (n=116) than in the non-exercise pulmonary hypertension group (n=133). Lower peak oxygen consumption (13.5±3.8 versus 16.6±4.7 mL·min^-1·kg^-1; p<0.001) was observed in the former group. The mPAP-CO slope was negatively correlated with peak oxygen consumption (r= -0.45, p<0.001) and positively correlated with the minute ventilation versus carbon dioxide output slope (r=0.39, p<0.001).

CONCLUSIONS

Impaired exercise capacity and ventilatory efficiency were observed in patients with CTEPH who had normalised PAP at rest but exercise pulmonary hypertension.

Pulse wave transit time during exercise testing reflects the severity of heart disease in cardiac patients

The pulse wave transit time (PWTT) is easily measured as the time from the R wave of an electrocardiogram to the arrival of the pulse wave measured by an oxygen saturation monitor at the earlobe. We investigated whether the change of PWTT during exercise testing reflects cardiopulmonary function. Eighty-nine cardiac patients who underwent cardiopulmonary exercise testing (CPX) were enrolled. We analyzed the change of PWTT during exercise and the relationship between the shortening of the PWTT and CPX parameters. PWTT was significantly shortened from rest to peak exercise (204.6 ± 33.6 vs. 145.6 ± 26.4 msec, p < 0.001) in all of the subjects. The patients with heart failure had significantly higher PWTT at peak exercise than the patients without heart failure (152.7 ± 27.1 vs. 140.4 ± 24.8 msec, p = 0.031). The shortening of PWTT from rest to peak exercise showed significant positive correlations with the peak O₂ uptake (VO₂) (r = 0.56, p < 0.001), anaerobic threshold (r = 0.40, p = 0.016), and % increase of systolic blood pressure during exercise (r = 0.75, p < 0.001), and a negative correlation with the slope of the increase in ventilation versus the increase in CO₂ output (VE-VCO₂ slope) (r = - 0.42, p = 0.010) in the patients with heart failure. PWTT was shortened during exercise as the exercise intensity increased. In the patients with heart failure, the shortening of PWTT from rest to peak exercise was smaller in those with lower exercise capacity and those with higher VE-VCO₂ slope, an established index known to reflect the severity of heart failure.

The role of cardiopulmonary exercise testing and training in patients with pulmonary hypertension: making the case for this assessment and intervention to be considered a standard of care

Introduction: Pulmonary hypertension (PH) is a broad pathophysiological disorder primarily characterized by increased pulmonary vascular resistance due to multiple possible etiologies. Patients typically present with multiple complaints that worsen as disease severity increases. Although initially discouraged due to safety concerns, exercise interventions for patients with PH have gained wide interest and multiple investigations have established the effective role of exercise training in improving the clinical profile, exercise tolerance, and overall quality of life.Areas covered: In this review, we discuss the pathophysiology of PH during rest and exercise, the role of cardiopulmonary exercise testing (CPX) in the diagnosis and prognosis of PAH, the role of exercise interventions in this patient population, and the expected physiological adaptations to exercise training.Expert opinion: Exercise testing, in particular CPX, provides a wealth of clinically valuable information in the PH population. Moreover, the available evidence strongly supports the safety and efficacy of exercise training as a clinical tool in improving exercise tolerance and quality of life. Although clinical trials investigating the role of exercise in this PH population are relatively few compared to other chronic conditions, current available evidence supports the clinical implementation of exercise training as a safe and effective treatment modality.

Etiology of Exercise-Induced Pulmonary Hypertension Can Be Differentiated by Echocardiography - Insight From Patients With Chronic Pulmonary Thromboembolism With Normal Resting Hemodynamics by Balloon Pulmonary Angioplasty

BACKGROUND

Exercise-induced pulmonary hypertension (PH) is often seen in chronic thromboembolic PH (CTEPH) patients with normalized resting hemodynamics, but it is difficult to differentiate precapillary PH as pulmonary vascular dysfunction and post-capillary PH from occult-left ventricular dysfunction (LVD). The aim of this study was to examine whether the exercise-induced elevation of pulmonary arterial wedge pressure (PAWP) can be predicted by the echocardiographic index at rest.Methods and Results:A total of 71 CTEPH patients (67±11 years old, male/female=15/56) treated by pulmonary angioplasty with near-normal pulmonary arterial pressure (PAP) and normal PAWP at rest underwent symptom-limited exercise test using supine cycle ergometer with right heart catheterization. Exercise-induced elevation in PAWP of >20 mmHg during exercise was defined as occult-LVD. Resting echocardiography was performed within 3 months. In the occult-LVD (n=28), PAWP at rest after leg raising for exercise (14±4 vs. 11±3 mmHg, P<0.001), and mean PAP during exercise were higher compared with the non-LVD (n=43). Peak oxygen consumption, cardiac output, and pulmonary vascular resistance at peak exercise did not differ between groups. Left atrial volume index (LAVi) in the occult-LVD was significantly larger (39.7±8.1 vs. 34.4±9.6 mL/m², P=0.017). LAVi correlated with exercise PAWP (r=0.356, P=0.002), but not resting PAWP (r=0.161, P=0.179).

CONCLUSIONS

Larger left atrial volume may reflect the exercise-induced PAWP elevation as occult-LVD in CTEPH patients.

Clinical significance of respiratory compensation during exercise testing in cardiac patients

Ventilation (VE) increases linearly with the increase of carbon dioxide output (VCO2) during cardiopulmonary exercise testing. VE-VCO2 slope rises in parallel with exercise intensity, reaches a turning point (called the RC point), then steepens because of respiratory compensation for lactic acidosis. While this RC point can be identified universally, it is undetectable in some patients. In this study we evaluated whether the respiratory compensation during exercise testing has clinical significance in cardiac patients. In total, 152 cardiac patients with a respiratory exchange ratio at peak exercise (peak R) of between 1.10 and 1.20 were enrolled. Cardiopulmonary parameters were compared between patients who manifested the RC point (n = 118) and those who did not (n = 34). The peak R did not significantly differ between these two groups. Compared to the patients without the RC point, those with the RC point had a higher oxygen uptake at peak exercise (peak VO2) (20.2 ± 5.3 vs 13.6 ± 3.4 mL/min/kg, p < 0.001), higher anaerobic threshold (AT) (12.4 ± 3.2 vs 9.2 ± 2.3 mL/min/kg, p < 0.001), and lower VE-VCO2 slope (31.7 ± 5.8 vs 37.8 ± 9.6, p = 0.001). Brain natriuretic peptide (BNP) tended to be lower in the patients with the RC point (175.4 ± 364.7 vs 327.9 ± 381.1 pg/mL, p = 0.067). Peak VO2, the marker of cardiopulmonary function, was found to be the independent predictor of the presence of the RC point. The present findings suggest that the phenomenon of respiratory compensation during heavy exercise indicates better cardiopulmonary function in cardiac patients within a prescribed range of effort.

Clinical significance of a spiral phenomenon in the plot of CO₂ output versus O₂ uptake during exercise in cardiac patients

A spiral phenomenon is sometimes noted in the plots of CO₂ output (VCO₂) against O₂ uptake (VO₂) measured during cardiopulmonary exercise testing (CPX) in patients with heart failure with oscillatory breathing. However, few data are available that elucidate the clinical significance of this phenomenon. Our group studied the prevalence of this phenomenon and its relation to cardiac and cardiopulmonary function. Of 2,263 cardiac patients who underwent CPX, 126 patients with a clear pattern of oscillatory breathing were identified. Cardiopulmonary indexes were compared between patients who showed the spiral phenomenon (n = 49) and those who did not (n = 77). The amplitudes of VO₂ and VCO₂ oscillations were greater and the phase difference between VO₂ and VCO₂ oscillations was longer in the patients with the spiral phenomenon than in those without it. Patients with the spiral phenomenon also had a lower left ventricular ejection fraction (43.4 ± 21.4% vs 57.1 ± 16.8%, p <0.001) and a higher level of brain natriuretic peptide (637.2 ± 698.3 vs 228.3 ± 351.4 pg/ml, p = 0.002). The peak VO₂ was lower (14.5 ± 5.6 vs 18.1 ± 6.3, p = 0.002), the slope of the increase in ventilation versus VCO₂ was higher (39.8 ± 9.5 vs 33.6 ± 6.8, p <0.001), and end-tidal PCO₂ both at rest and at peak exercise was lower in the patients with the spiral phenomenon than in those without it. In conclusion, the spiral phenomenon in the VCO₂-versus-VO₂ plot arising from the phase difference between VCO₂ and VO₂ oscillations reflects more advanced cardiopulmonary dysfunction in cardiac patients with oscillatory breathing.

Prognostic value of cardiopulmonary exercise testing in cardiac patients with atrial fibrillation

Parameters obtained from cardiopulmonary exercise testing (CPX) are recognized for their high prognostic value in predicting future cardiac events in cardiac patients. Our group compared the prognostic value of CPX parameters between patients with sinus rhythm (SR) and patients with atrial fibrillation (AF).Peak O2 uptake (VO2), the ratio of the increase in VO2 to the increase in work rate (ΔVO2/ΔWR), and the slope of the increase in ventilation to the increase in CO2 output (VE-VCO2 slope) were obtained from CPX in 72 AF patients and 478 SR patients. The prognostic values of these indices were compared between the two groups.Six cardiac deaths and 25 cardiac events were observed in the AF group and 9 cardiac deaths and 96 cardiac events were observed in the SR group, over a prospective follow-up period of 1,192 days. The percentages of cardiac deaths and cardiac events were higher in the AF group than in the SR group. In a multivariate Cox proportional hazards analysis, peak VO2 was identified as a sole significant predictor of cardiac death and cardiac events in SR patients and VE-VCO2 slope was identified as a sole significant predictor of cardiac death and cardiac events in AF patients.Our results suggest that the VE-VCO2 slope is strongly predictive of future cardiac events in patients with AF and that peak VO2 is strongly predictive of future cardiac events in SR patients.

Overshoot phenomena of respiratory gas variables during exercise recovery in cardiac patients

BACKGROUND

Transient increases (overshoot) in respiratory gas variables have been observed during exercise recovery, but their clinical significance is not clearly understood. Our group evaluated the relationship between the presence of overshoot of respiratory gas variables and the parameters obtained from cardiopulmonary exercise testing (CPX).

METHODS AND RESULTS

In total, 227 patients with various cardiac diseases underwent CPX. The overshoot phenomena of O₂ uptake (·VO₂), ·VO₂/heart rate (O₂-pulse), and CO₂ output (·VCO₂) were analyzed by respiratory gas analysis during recovery after maximal exercise. The overshoot of ·VO₂, O₂-pulse, and ·VCO₂ were recognized in 11 (5%), 43 (19%), and 12 (5%) patients, respectively. Compared with the patients without a ·VO₂ overshoot, those with a ·VO₂ overshoot had a significantly lower peak ·VO₂ (12.3±3.7 vs. 17.9±6.2ml·min⁻¹·kg⁻¹, P=0.003), lower anaerobic threshold (9.4±1.7 vs. 12.4±3.3 ml·min⁻¹·kg⁻¹, P=0.001), higher ·VE-·VCO₂ slope (38.0±5.2 vs. 33.2±9.6, P=0.013), and lower left ventricular ejection fraction (LVEF) (39.9±22.8 vs. 55.8±16.8%, P=0.003). Similar findings were obtained for the patients with an O₂-pulse overshoot and those with a ·VCO₂ overshoot.

CONCLUSIONS

The overshoot phenomena of respiratory gas variables during recovery after maximal exercise are correlated with impaired cardiopulmonary function during exercise in cardiac patients.

Association between right ventricular two-dimensional strain and exercise capacity in patients with either idiopathic or ischemic dilated cardiomyopathy

OBJECTIVES

To detect right ventricular myocardial function in dilated cardiomyopathy (DCM) using two-dimensional strain echocardiography (2DSE) and to evaluate the relationship between right ventricular dysfunction and response to cardiopulmonary exercise test (CPET).

METHODS

Seventy-five DCM patients (44 idiopathic and 31 ischemic) without clinical signs of right ventricular failure underwent standard echo, 2DSE analysis of right ventricle and bicycle CPET.

RESULTS

The two groups were comparable for clinical and standard two-dimensional echocardiographic and Doppler variables, except for right ventricular diameters that were mildly increased in patients with idiopathic DCM. Right ventricular global longitudinal strain (RV GLS) and regional peak myocardial right ventricular strain were significantly impaired in patients with idiopathic DCM compared with ischemic DCM (both P<0.001). A significant correlation was detectable among RV GLS and VO2 peak percentage (r= -0.65, P<0.0001), VE/VCO2 slope (r=0.35, P<0.01), maximum work rate percentage (r= -0.55, P<0.001) and peak circulatory power (r=0.53, P<0.001). These correlations with RV GLS remained significant even in multivariate analysis.

CONCLUSION

2DSE represents a promising noninvasive technique to assess right ventricular myocardial function in patients with DCM. Reduced right ventricular myocardial deformation is related to decreased ability to perform aerobic exercise and work rate, and to impaired ventilatory response.

Abnormal end-tidal PO(2) and PCO(2) at the anaerobic threshold correlate well with impaired exercise gas exchange in patients with left ventricular dysfunction

BACKGROUND

The aim of the present study was to compare the end-tidal O(2) pressure (PETO(2)) to end-tidal CO(2) pressure (PETCO(2)) in cardiac patients during rest and during 2 states of exercise: at anaerobic threshold (AT) and at peak. The purpose was to see which metabolic state, PETO(2) or PETCO(2), best correlated with exercise limitation.

METHODS AND RESULTS

Thirty-eight patients with left ventricular (LV) ejection fraction <40% underwent cardiopulmonary exercise testing (CPX). PETO(2) and PETCO(2) were measured during CPX, along with peak O(2) uptake (VO(2)), AT, slope of the increase in ventilation (VE) relative to the increase in CO(2) output (VCO(2)) (VE vs. VCO(2) slope), and the ratio of the increase in VO(2) to the increase in work rate (ΔVO(2)/ΔWR). Both PETO(2) and PETCO(2) measured at AT were best correlated with peakVO(2), AT, ΔVO(2)/ΔWR and VE vs. VCO(2) slope. PETO(2) at AT correlated with reduced peak VO(2) (r=-0.60), reduced AT (r=-0.52), reduced ΔVO(2)/ΔWR (r=-0.55) and increased VE vs. VCO(2) slope (r=0.74). PETCO(2) at AT correlated with reduced peak VO(2) (r=0.67), reduced AT (r=0.61), reduced ΔVO(2)/ΔWR (r=0.58) and increased VE vs. VCO(2) slope (r=-0.80).

CONCLUSIONS

PETCO(2) and PETO(2) at AT correlated with peak VO(2), AT and ΔVO(2)/ΔWR, but best correlated with increased VE vs. VCO(2) slope. PETO(2) and PETCO(2) at AT can be used as a prime index of impaired cardiopulmonary function during exercise in patients with LV failure.

Impact of diabetes on muscle mass, muscle strength, and exercise tolerance in patients after coronary artery bypass grafting

BACKGROUND

The impact of diabetes mellitus (DM) on muscle mass, muscle strength, and exercise tolerance in patients who had undergone coronary artery bypass grafting (CABG) has not been fully elucidated.

METHODS

We enrolled 329 consecutive patients who received cardiac rehabilitation (CR) after CABG (DM group, n=178; non-DM group, n=151) and measured lean body weight, mid-upper arm muscle area (MAMA), and handgrip power (HGP) at the beginning of CR. We also performed an isokinetic strength test of the knee extensor (Ext) and flexor (Flex) muscles and a cardiopulmonary exercise testing at the same time.

RESULTS

No significant differences in risk factors, including age, gender, number of diseased vessels, or ejection fraction were observed between the 2 groups. The levels of Ext muscle strength, peak oxygen uptake, and anaerobic threshold were significantly lower in the DM group than in the non-DM group (all p<0.05). Both peak oxygen uptake and MAMA correlated with Ext and Flex muscle strength as well as HGP (all p<0.005). The MAMA, HGP, and Ext muscle strength were lower in patients who received insulin therapy than in those who did not. Interestingly, fasting glucose levels significantly and negatively correlated with Ext muscle strength.

CONCLUSIONS

These data suggest that DM patients had a lower muscle strength and exercise tolerance than non-DM patients. Moreover, a high glucose level may affect these deteriorations in DM patients after CABG.

Effects of prolonged expiration breathing on cardiopulmonary responses during incremental exercise

This study was designed to clarify the effects of breathing with prolonged expiration on cardiopulmonary responses and autonomic nervous activity during incremental exercise. Eleven healthy men were randomly assigned to breathing mode: a prolonged expiration breathing with a 2-s inspired time and 4-s expired time and a spontaneous breathing without any constraints. Oxygen uptake (V(O2)), ventilation efficiency (V(E)/V(CO2)) and rate pressure product were measured. Low- (LF) and high-frequency (HF) components of blood pressure and heart rate variability were analyzed to assess sympathetic and parasympathetic nervous activities, respectively. V(E)/V(CO2), rate pressure product and LF were significantly lower, and [Formula: see text] and HF were significantly higher during exercise with prolonged expiration than with spontaneous breathing. Striking effects of prolonged expiration breathing included the improvement of ventilation efficiency, the suppression of sympathetic nervous activity and the activation of parasympathetic one during incremental exercise. Furthermore, prolonged expiration breathing may have suppressed the exercise-induced increase in myocardial V(O2).

Submaximal exercise gas exchange is an important prognostic tool to predict adverse outcomes in heart failure

AIMS

Traditionally, VO(2peak) has been used to determine prognosis in heart failure; however, this measure has limitations. Hence, other exercise and gas exchange parameters measured submaximally, e.g. breathing efficiency (V(E)/VCO(2)), end-tidal CO(2) (P(ET)CO(2)), oxygen uptake efficiency slope (OUES), and circulatory power [ systolic blood pressure (SBP)], have been investigated. The aim of this study was to investigate the prognostic relevance of submaximal exercise gas exchange in heart failure patients. Method and results One hundred and thirty-two consecutive heart failure patients (mean age 56 ± 12 years, ejection fraction 29 ± 11%) performed peak treadmill testing. Gas exchange and haemodynamic variables were measured continuously. Gas exchange data obtained from the first 2 min of exercise and at a respiratory exchange ratio (RER) of 0.9 were the measurements of interest. Over a median follow-up period of 62.4 (range 0-114) months, there were 44 endpoints (death or transplant). Univariate analysis demonstrated submaximal predictors of survival, which included V(E)/VCO(2) slope and ratio, P(ET)CO(2), OUES, and circulatory power (P ≤ 0.01). When these and additional submaximal variables were included together in the multivariable analysis, the strongest submaximal exercise predictive model (C-statistic 0.75) comprised data from the first stage of exercise (V(E) and circulatory power) and at an RER of 0.9 (V(E)/VCO(2) ratio). The inclusion of VO(2 peak) and demographic data, with submaximal data (V(E)/VCO(2) ratio at an RER = 0.9), increased the predictiveness of the model (C-statistic 0.78).

CONCLUSION

Submaximal exercise measures provide useful prognostic information for predicting survival in heart failure. This form of testing is logistically easier, cheaper, and safer for patients compared with maximal exercise.

Causes of breathing inefficiency during exercise in heart failure

BACKGROUND

Patients with heart failure (HF) develop abnormal pulmonary gas exchange; specifically, they have abnormal ventilation relative to metabolic demand (ventilatory efficiency/minute ventilation in relation to carbon dioxide production [V(E)/VCO₂]) during exercise. The purpose of this investigation was to examine the factors that underlie the abnormal breathing efficiency in this population.

METHODS AND RESULTS

Fourteen controls and 33 moderate-severe HF patients, ages 52 ± 12 and 54 ± 8 years, respectively, performed submaximal exercise (∼65% of maximum) on a cycle ergometer. Gas exchange and blood gas measurements were made at rest and during exercise. Submaximal exercise data were used to quantify the influence of hyperventilation (PaCO₂) and dead space ventilation (V(D)) on V(E)/VCO₂. The V(E)/VCO₂ relationship was lower in controls (30 ± 4) than HF (45 ± 9, P < .01). This was the result of hyperventilation (lower PaCO₂) and higher V(D)/V(T) that contributed 40% and 47%, respectively, to the increased V(E)/VCO₂ (P < .01). The elevated V(D)/V(T) in the HF patients was the result of a tachypneic breathing pattern (lower V(T), 1086 ± 366 versus 2003 ± 504 mL, P < .01) in the presence of a normal V(D) (11.5 ± 4.0 versus 11.9 ± 5.7 L/min, P = .095).

CONCLUSIONS

The abnormal ventilation in relation to metabolic demand in HF patients during exercise was due primarily to alterations in breathing pattern (reduced V(T)) and excessive hyperventilation.

Overshoot phenomenon of oxygen uptake during recovery from maximal exercise in patients with previous myocardial infarction

The overshoot in oxygen uptake (VO2 overshoot) during recovery from maximal exercise is thought to reflect an overshoot in cardiac output. We investigated whether this phenomenon is related to cardiopulmonary function during exercise in cardiac patients. A total of 201 consecutive patients with previous myocardial infarction underwent cardiopulmonary exercise testing (CPX). An apparent VO2 overshoot during the recovery from CPX (6.5+/-8.1% increase relative to the peak VO2) was observed in ten patients. A comparison of patients with the VO2 overshoot to those without the VO2 overshoot revealed that the former had a significantly lower left ventricular ejection fraction (40.1+/-19.1 vs. 55. 2+/-14.9%, respectively, p = 0.002) and larger left ventricular diastolic and systolic dimensions. Patients with the VO2 overshoot also had a significantly lower peak VO2 (13.1+/-6.1 vs. 18.1+/-4.5 ml/min/kg, p < 0.001), lower DeltaVO2/DeltaWR (work rate) (6.6+/-3.8 vs. 9.5+/-1.7 mL/min/W, p < 0.0001), and a higher E (minute ventilation)/VCO2 (carbon dioxide output) slope (45.0+/-18.6 vs. 32.6+/-6.6, p < 0.0001) than those without the overshoot. A VO2 overshoot during recovery from maximal exercise was found in 5% of patients with previous myocardial infarction. This condition, which suggests a transient mismatch between cardiac contractility and afterload reduction, was found to be related to impaired cardiopulmonary function during exercise.

Ventilatory expired gas at constant-rate low-intensity exercise predicts adverse events and is related to neurohormonal markers in patients with heart failure

BACKGROUND

Ventilatory efficiency (VE/VCO(2) ratio) and the partial pressure of end-tidal carbon dioxide (P(ET)CO(2)), obtained during moderate to high levels of physical exertion demonstrate prognostic value in heart failure (HF). The present investigation assesses the clinical utility of these variables during low-intensity exercise.

METHODS AND RESULTS

One hundred and thirty subjects diagnosed with HF underwent a 2-minute, constant-rate treadmill session at 2 miles per hour. Both the VE/VCO(2) ratio and P(ET)CO(2) were recorded during exercise (30-second average) and their change (Delta) from rest. B-type and atrial natriuretic peptide (BNP and ANP) were also determined. Only P(ET)CO(2) and DeltaP(ET)CO(2) emerged from the multivariate Cox regression. Receiver operating characteristic curve analysis revealed the prognostic classification schemes were significant with thresholds of < or >or=34 mm Hg (hazard ratio: 4.2, 95% CI: 2.2-8.0, P < .001) and < or >or=1 mm Hg (hazard ratio: 3.5, 95% CI: 1.9-6.6, P < .001) being optimal for P(ET)CO(2) and DeltaP(ET)CO(2), respectively. Moreover, subjects with a P(ET)CO(2)>or=34 mm Hg had a significantly lower BNP (214.1 +/- 431.9 vs. 1110.5 +/- 1854.0 pg/mL, P=.005) and ANP (108.2 +/- 103.6 vs. 246.2 +/- 200.4 pg/mL, P < .001).

CONCLUSIONS

The results of this pilot study indicate ventilatory expired gas analysis during a short bout of low-intensity exercise may provide insight into prognosis and cardiac stability.

Prognostic value of end-tidal CO2 pressure during exercise in patients with left ventricular dysfunction

We compared the prognostic power of end-tidal CO(2) pressure (PETCO(2)) during exercise, an index of arterial CO(2) pressure, with those of established respiratory gas indexes during exercise testing in patients with left ventricular dysfunction. Seventy-eight consecutive patients with a left ventricular ejection fraction (LVEF) Collapse

Key Words

• end-tidal co₂ pressure
• peak \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{\rm{v}} $$\end{document}o₂
• exercise testing

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MESH Headings

• Aged
• Carbon Dioxide/metabolism
• Exercise/physiology
• Exercise Test/methods
• Female
• Follow-Up Studies
• Humans
• Kaplan-Meier Estimate
• Male
• Middle Aged
• Oxygen Consumption/physiology
• Predictive Value of Tests
• Prognosis
• Prospective Studies
• ROC Curve
• Respiratory Function Tests/methods
• Risk Factors
• Stroke Volume/physiology
• Ventricular Dysfunction, Left/diagnosis
• Ventricular Dysfunction, Left/mortality
• Ventricular Dysfunction, Left/physiopathology

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Grants Collapse

Affiliation(s)

Masayo Hoshimoto-Iwamoto The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan School of Health and Sports Science, Juntendo University, Chiba, Japan
Akira Koike The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan
Osamu Nagayama The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan
Akihiko Tajima The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan
Takeya Suzuki Department of Cardiovascular Medicine, Toho University Omori Medical Center, Tokyo, Japan
Tokuhisa Uejima The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan
Hitoshi Sawada The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan
Tadanori Aizawa The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan

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Clinical significance of cerebral oxygenation during exercise in patients with coronary artery disease

BACKGROUND

Recent investigations have demonstrated that cerebral oxyhemoglobin (O(2)Hb) decreases during exercise in patients with left ventricular dysfunction, reflecting a cerebral hypoxia. We sought to establish a prognostic value of decreased cerebral O(2)Hb during exercise in cardiac patients, and to compare it with those of indexes obtained from cardiopulmonary exercise testing (CPX).

METHODS AND RESULTS

A total of 344 consecutive patients with coronary artery disease were enrolled in the study. All the patients performed CPX, during which cerebral O(2)Hb was continuously monitored using near-infrared spectroscopy. There were 13 cardiac deaths and 78 cardiovascular events during the prospective follow-up period of 1,231+/-538 days. The change of O(2)Hb measured at the forehead from rest to peak exercise (DeltaO(2)Hb) was significantly lower in non-survivors than in survivors (-1.5+/-3.3 vs 1.7+/-3.2 micromol/L, p=0.0004). By multivariate Cox proportional hazards analysis, DeltaO(2)Hb and left ventricular ejection fraction (LVEF) were found to be independent prognostic markers for cardiac deaths. The DeltaO(2)Hb, LVEF and peak oxygen uptake were found to be significant prognostic markers for cardiovascular events, mainly for heart failure worsening and sudden cardiac death.

CONCLUSION

The present findings suggest that a decrease in cerebral O(2)Hb during exercise predicts future cardiovascular events in patients with coronary artery disease.

Peak VO(2) is more potent than B-type natriuretic peptide as a prognostic parameter in cardiac patients

BACKGROUND

It is well-known that both B-type natriuretic peptide (BNP) and peak oxygen uptake (VO(2)) are independent predictors of mortality in patients with heart failure. This study investigates the predictive power of BNP and peak VO(2) for survival in cardiac patients.

METHODS AND RESULTS

A total of 609 patients with cardiac disease participated in the study. They underwent cardiopulmonary exercise testing to determine peak VO(2), with BNP being measured before exercise testing During 502.5 median follow-up days, 29 patients died of cardiovascular disease. In the univariate Cox proportional hazards analysis, peak VO(2) and BNP were both found to be significant prognostic indices for survival. The time-dependent ROC curve analysis (Heagerty 2006) was applied to 3 predictors: peak VO(2), BNP, and then both, with gender and age as adjusted variables. The area under the curve (AUC) compared with the follow-up period curves of peak VO(2) and the 2 combined variables (ie, BNP and peak VO(2)) were consistently over that of BNP. The integrated AUC indices were 0.80 (peak VO(2)), 0.81 (peak VO(2) and BNP) and 0.70 (BNP), respectively.

CONCLUSIONS

These results indicate that peak VO(2) is more potent than BNP for predicting the mortality in patients with mixed cardiac disease.

Effects of Supplemental O2 Inhalation on Cerebral Oxygenation During Exercise in Patients With Left Ventricular Dysfunction

BACKGROUND

It has been recently reported that cerebral oxyhemoglobin (O(2)Hb) decreases during exercise in nearly 50% of patients with dilated cardiomyopathy. The present study evaluated whether the inhalation of supplemental O(2) diminishes the decrease in cerebral O(2)Hb during exercise.

METHODS AND RESULTS

Ten patients with a left ventricular ejection fraction <50% and a clearly observable decrease in cerebral O(2)Hb during preliminary exercise testing underwent 2 additional symptom-limited incremental exercise tests: 1 while breathing room air (control) and the other while breathing 50% O(2). In the latter test, the switch from room air to 50% O(2) was performed, on average, at 43.0+/-14.2 W. Cerebral O(2)Hb was continuously monitored during exercise using near-infrared spectroscopy. In the control exercise test, cerebral O(2)Hb gradually decreased as the work rate increased in all the subjects. When the subjects breathed 50% O(2), this decrease in cerebral O(2)Hb was diminished. The change in cerebral O(2)Hb from rest to peak exercise during the test under 50% O(2) was significantly higher than that during the control test (-0.23 +/-1.89 vs -2.47+/-1.57 micromol/L, p=0.002). Similarly, the change in the cerebral tissue oxygenation index was significantly higher in the test under 50% O(2) (0.45 +/-4.46 vs -3.33+/-3.06%, p=0.023).

CONCLUSIONS

Impaired cerebral oxygenation during moderate to heavy intensity exercise in patients with left ventricular dysfunction can be offset by breathing supplemental O(2).

Influence of Cerebrovascular Arteriosclerosis on Cerebral Oxygenation During Exercise

BACKGROUND

Although it is assumed that cerebral oxygenation during exercise is influenced by both cardiopulmonary function and cerebrovascular arteriosclerosis, the latter factor has not been fully clarified. In the present study the relationship between the degree of cerebrovascular arteriosclerosis and cerebral oxygenation during exercise was investigated.

METHODS AND RESULTS

A total of 109 patients (69 patients with coronary artery disease, 40 patients with hypertensive heart disease) (61.7+/-9.7 years) performed a symptom-limited exercise test with respiratory gas measurements (CPX). From the respiratory gas analysis, peak O(2) uptake (VO(2)), the slope of the increase in VO(2) to the increase in work rate (DeltaVO (2)/DeltaWR), and the slope of the increase in ventilation to the increase in CO(2) output (VE/VCO(2) slope) were calculated. Oxyhemoglobin (O(2)Hb) at the forehead was monitored using near-infrared spectroscopy. The brain ischemic score was counted based upon fluid-attenuated inversion recovery images of magnetic resonance imaging and expressed from 0 to 4. When compared with patients with a lower ischemic score (<2, n=67), those with a higher ischemic score (> or =2, n=42) had a lower increase in brain O(2)Hb during exercise (-1.08 +/-2.7 vs 0.77+/-4.1 micromol/L, p=0.011). Of brain ischemic score, left ventricular ejection fraction, peak VO(2), DeltaVO(2)/DeltaWR, and the VE/VCO(2) slope, DeltaVO(2)/ DeltaWR was found to be the sole independent index determining cerebral O(2)Hb during exercise. The CPX parameters were also significantly related to the degree of cerebrovascular arteriosclerosis.

CONCLUSIONS

Although cerebral oxygenation during exercise is mainly related to cardiopulmonary function, the degree of cerebrovascular arteriosclerosis partly influences cerebral oxygenation in patients with risk factors for atherosclerosis.

Understanding the basics of cardiopulmonary exercise testing

Cardiopulmonary exercise testing adds important additional information to that provided by the standard exercise test. In particular, cardiopulmonary exercise testing provides precise determination of aerobic capacity, the causes of dyspnea with exertion, and prognosis in patients with systolic heart failure. This review provides basic, practical information about cardiopulmonary exercise testing for the clinician.

Standardizing and predicting results from cardiopulmonary exercise testing in patients with heart failure

PURPOSE

Cardiopulmonary exercise testing is a common prognostic tool in heart failure, yet it is not standardized. The purpose of this study was to evaluate a means of standardizing oxygen consumption (VO(2)) measurement and to evaluate the ability to predict peak VO(2) from submaximal exercise.

METHODS

Fifty consecutive exercise tests with a respiratory exchange ratio > or =1.10 were evaluated. VO(2) was graphed against respiratory exchange ratio and the peak VO(2) was determined with logarithmic, linear, power, and exponential regression lines. To predict a peak VO(2), each patient's submaximal exercise data (respiratory exchange ratio < or =0.98) were fitted to each regression line. The mean of the last 30 seconds of un-averaged breath-by-breath data was used as the reference value. Peak VO(2) assessments are also provided from the metabolic cart, a rolling time average, and the graphical method.

RESULTS

Logarithmic regression best standardized peak VO(2). Mean absolute bias (mL x kg x min) was 0.60 +/- 0.44 for logarithmic, 0.61 +/- 0.47 for linear, 0.85 +/- 0.67 for power, and 1.44 +/- 2.22 for exponential. The mean absolute bias between the peak logarithmic predicted VO(2) and the reference peak VO(2) was 1.62 +/- 1.20 mL x kg x min (9.5% of the peak VO(2)).

CONCLUSION

Among the methods studied, logarithmic regression analysis was the best method to standardize and predict peak VO(2) in this cohort of patients with heart failure.

Statement on cardiopulmonary exercise testing in chronic heart failure due to left ventricular dysfunction: recommendations for performance and interpretation. Part I: definition of cardiopulmonary exercise testing parameters for appropriate use in chronic heart failure

Cardiopulmonary exercise testing (CPET) provides a global assessment of the integrated response to exercise involving the pulmonary, cardiovascular, haematopoietic, neuropsychological, and skeletal muscle systems. This information cannot be obtained through investigation of the individual organ systems in isolation. The non-invasive, dynamic physiological overview permits the evaluation of both submaximal and peak exercise responses, providing the physician with relevant information for clinical decision making. The use of CPET in management of the chronic heart failure patient is increasing with the understanding that resting pulmonary and cardiac function testing cannot reliably predict exercise performance and functional capacity and that, furthermore, overall health status and prognosis are predicted better by indices of exercise tolerance than by resting measurements. Our aim is to produce a statement which provides recommendations on the interpretation and clinical application of CPET in heart failure, based on contemporary scientific knowledge and technical advances: the focus is on clinical indications, issues of standardization, and interpretative strategies for CPET.

[Exercise training in cardiac patients: usefulness of the cardiopulmonary exercise test]

Exercise training is currently including in the treatment of coronary arterial disease patients, in patients with left ventricular dysfunction as well as in patients who underwent cardiac transplantation or cardiac surgery. However methods of prescribing exercise-training programs are difficult to determine and must be adapted for each patient Exercise test with gas analysis through the determination of anaerobic threshold may help to understand the physiopathological mechanism related to exercise limitation in these patients. Exercise test may help to precise exercise intensity during cardiac rehabilitation and may assess the benefits on exercise tolerance.

Does the Severity of Central Sleep Apnea Correlate With Respiratory Gas Indexes During Cardiopulmonary Exercise Testing?

Central sleep apnea (CSA) is thought to arise as a consequence of chronic heart failure. We have attempted to determine the relationship between the severity of CSA and the respiratory gas indexes during cardiopulmonary exercise testing (CPX), indexes well-known to reflect the severity of heart failure. Twenty consecutive cardiac patients (59.0 +/- 15.3 years) with CSA underwent CPX. End-tidal PCO(2)(PETCO(2)) was measured at rest and at peak exercise as a substitute for PaCO(2), along with the peak oxygen uptake (V(.)O(2)) and the ratio of the increase in ventilation to the increase in CO(2)output (V(.)E/V(.)CO(2) slope). Peak VO(2), % peak VO(2), and the VE/V(.)CO(2) slope of the subjects were 15.5 +/- 5.8 mL/min/kg, 52.8 +/- 16.7%, and 37.9 +/- 12.5, respectively, showing moderate to severely decreased exercise capacity. While PETCO(2) at both rest and peak exercise significantly correlated with peak VO(2) (r = 0.63 and r = 0.51, respectively) and the VE/V(.)CO(2) slope (r = -0.77 and r = -0.91, respectively), none of these 3 parameters correlated with the apnea-hypopnea index. The apnea-hypopnea index in the subjects with lower resting PETCO(2) was not notably different from that in the subjects with relatively high PETCO(2). Although the severity of CSA is assumed to correlate with the severity of heart failure, and a lowering of PaCO(2) during wakefulness is considered to be one of the mechanisms behind CSA, the severity of CSA does not correlate with the respiratory gas indexes of CPX or the level of PETCO(2) in cardiac patients with moderate to severely decreased exercise capacity.